Model-Independent Bound on the Dark Matter Lifetime

TL;DR

This paper establishes a conservative, model-independent lower bound on dark matter lifetime by considering decays into neutrinos, avoiding assumptions about specific decay modes or radiative processes.

Contribution

It introduces a new, model-independent method to constrain dark matter lifetime based solely on neutrino flux limits from the Milky Way.

Findings

Neutrino flux limits set stringent bounds on DM lifetime.

Model-independent bounds are comparable to or better than radiative decay constraints.

Assumption that DM decays into at least one SM particle, specifically neutrinos.

Abstract

If dark matter (DM) is unstable, in order to be present today, its lifetime needs to be longer than the age of the Universe, t_U ~ 4 10^{17} s. It is usually assumed that if DM decays it would do it with some strength through a radiative mode. In this case, very constraining limits can be obtained from observations of the diffuse gamma ray background. However, although reasonable, this is a model-dependent assumption. Here our only assumption is that DM decays into, at least, one Standard Model (SM) particle. Among these, neutrinos are the least detectable ones. Hence, if we assume that the only SM decay daughters are neutrinos, a limit on their flux from DM decays in the Milky Way sets a conservative, but stringent and model-independent bound on its lifetime.